Systems for monitoring force loads are well known and are used with a variety of products to determine structural conditions in mechanical components. These systems are characterized by a plurality of parameter sensors, such as strain gauges, which are positioned locally with the mechanical elements and provide signals to a remote processor. The measured data is correlated by the processor in accordance with a pre-established relationship. The processor output signals are indicative of the stress or loading conditions of the elements.
In many applications, the direct instrumentation of mechanical elements is possible. For example, strain gauges and sensors can easily be positioned locally on an airplane's wings and aerilons, with signals from the sensors conventionally routed to a remote cockpit processor. However, for some elements, such as rotating turbine blades in a jet engine, direct instrumentation is impossible or impractical. Another such example is a rotating helicopter blade. Direct instrumentation of the blade with locally positioned sensors can only be accomplished by employing a sophisticated slip ring apparatus which is prone to wear and must therefore be maintained on a frequent basis. As a result, remote blade mounted instrumentation is configured with a helicopter only for purposes of initial testing and calibration.
Techniques for indirectly measuring structural parameters of loaded mechanical elements have also been explored. With these techniques, sensors are remotely positioned from the loaded components of interest. For example, in an airplane, a plurality of sensors can be positioned on the aircraft body. The signal received at these sensors comprises a component due to the loading of the airplane body, as well as a component indicative of the loads on the aircraft wings. Using pre-determined relationships, a processor could ideally isolate the strain information from the element of interest and correlate that data to the loading of the element. To date, no system has demonstrated a consistent capability of extracting desired loading information using signals from remotely positioned sensors.
Determining the signal component output loads on helicopter elements are additonally more since the loads imposed upon the various rotating elements are periodic. Systems which have attempted to remotely determine structural parameters in the rotating elements of a helicopter, such as blade strains or moments, have been unsuccessful because the mathematical computations required have been deemed too complex and that the requisite data is insufficiently measurable. It would be desirable to have a system which remotely senses loads on structural elements of a mechanical system and would establish correlation between measured parameters and desired values using matrix methods for correlative regression and information processing in reeal-time, with a minimal sensor signal input generating a fixed data stream. The present invention is drawn towards such a system.